Transducers convert signals from one domain to another and are often used in sensors. A common transducer used as a sensor that is seen in everyday life is a microphone, a sensor for audio signals with a transducer that converts sound waves to electrical signals.
Microelectromechanical system (MEMS) based sensors include a family of transducers produced using microfabrication techniques. MEMS, such as a MEMS microphone, gather information from the environment through measuring physical phenomena, and electronics attached to the MEMS then process the signal information derived from the sensors. MEMS devices may be manufactured using micromachining fabrication techniques similar to those used for integrated circuits.
Audio microphones are commonly used in a variety of consumer applications such as cellular telephones, digital audio recorders, personal computers and teleconferencing systems. In a MEMS microphone, a pressure sensitive diaphragm is disposed directly onto a semiconductor die, for example. As such, the microphone is formed as a MEMS die using microfabrication techniques, rather than being fabricated from individual discrete parts.
MEMS devices may be formed as oscillators, resonators, accelerometers, gyroscopes, pressure sensors, microphones, microspeakers, micro-mirrors, and other devices, and often use capacitive sensing techniques for measuring the physical phenomenon being measured. In such applications, the capacitance change of the capacitive sensor is converted into a usable voltage or current using interface circuits. In order to properly operate such capacitive sensors, the interface circuits may include biasing elements, such as a charge pump, and sensing elements, such as resistors, capacitors, and amplifiers. The design and manufacture of the interface circuit introduces numerous characteristics to the capacitive sensor behavior. Thus, there exists opportunity for novel or improved interface circuit elements for application to transducers or other capacitive circuits.